The Fader to Zero function in Logic is not working with the latest update from Apple.
It appears that Logic's implementation of MCU has changed; we have contacted Apple to raise their awareness of this.
Follow this article for updates.
In Logic 10.8 this feature has been added but to the Opt key.
On your UF8 this is mapped to the soft key page 3 key 2. Press and hold this and select the channel that you want to Zero
On the UF1 this is soft key page 5 and key 2.